The present invention relates to marine engines having a lower gearcase which normally operates partially submerged in water and provides an improvement in my invention set forth in my U.S. patent application Ser. No. 144,329 now U.S. Pat. No. 4,757,710.
A major source of trouble occurring with such marine engines is the entry of water into the lower gearcase, especially when the engines are operated in salt water. Water leaking into the gearcase mixes with the liquid lubricant within the gearcase and drastically reduces the lubricant's effectiveness. The water also tends to pit the surfaces of the moving metal parts of the power train and these effects eventually cause failure of the power train and costly repair and replacement of damaged parts.
Up to now the only way to guard against damages caused by the entry of water into the lower gearcase of marine engines has been to periodically take the marine engine out of the water, drain the lubricant and thus determine whether or not the lubricant has been contaminated with water. Such procedure conventionally recommended by the manufacturers of most marine engines, is both costly and time consuming. To take a medium sized sport fishing boat out of the water and check the condition of its outboard marine engine, most marinas charge in excess of $100 plus the cost of materials and supplies used.
My invention provides a sight glass or window in the side of the lower gearcase of a marine engine. The presence of even a few cubic centimeters of water mixed into the conventional liquid lubricant contained within the lower gearcase of a small outboard engine will turn the lubricant from its normally dark brown color to a milky-off white.
Thus by use of my invention the boat's owner or operator can look into the sight glass in the side of the gearcase and immediately determine by observing the color of the lubricant within the gearcase whether or not water has leaked into the lower gearcase. My sight glass permits frequent inspection of the interior of the gearcase without cost or removal of the boat from the water. It also permits prompt corrective action to be taken in the event water has entered the gearcase, thus saving expensive repairs or replacement which would have resulted if the water had remained in the gearcase for an extended period of time.
My present invention is especially designed for use by the manufacturers of marine engines. I recommend that the lower gearcase housing be cast with a circular opening having a thickness about double the usual thickness of the housing in the side of the casing. The outer edge of this hole can then be machined and threaded to accept the three elements of my sight glass assembly.
My sight glass assembly includes an O-ring, a disc-shaped sight glass and a window cover which is threaded to fit into the internally threaded circular opening in the gearcase housing. The opening in the gearcase housing contains an axially concentric groove into which is fitted the O-ring of resilient waterproof material. Then the preferably flat circular transparent sight glass is pressed against the O-ring and firmly locked into waterproof connection with the O-ring by the window cover which is pressed against the outer edge of the sight glass opposite to the outer edge of the sight glass which is pressed against the O-ring.
The window cover is threadedly joined to the gearcase housing and preferably locked into place by a lock screw threaded into a hole located in the adjoining outer edges of the gearcase housing and the window cover.
I have found the foregoing sight glass assembly to be absolutely waterproof in tests with no leakage of water into the engine's gearcase.